1. Field of Invention
The invention relates to a vehicle wiper apparatus for use in trucks, passenger cars and other vehicles.
2. Description of Related Art
In general, one such vehicle wiper apparatus is equipped with a link rod reciprocating in its longitudinal directions in response to a driving force from a wiper motor, a wiper shaft fixedly holding a wiper arm and supported on a body side to be rotatable around its axis, and a link arm whose proximal portion is fixedly secured integrally to the wiper shaft and whose tip portion is pivotally supported by a tip portion of the link rod to be swingable, with the wiper arm of the wiper shaft being made to take reciprocating and wiping action in conjunction with reciprocative swinging movements of the link arm around the wiper shaft by reciprocating movements of the link rod.
The wiper apparatus is designed so that the rotation angle of the wiper shaft, that is, the swinging angle of the link arm, directly corresponds to the wiping swinging angle of the wiper arm, and a tendency is toward setting the swinging angle of the link arm to a large value for the purpose of securing a large window surface wiping area. On the other hand, in this case, there is a possibility that the swinging of the link arm exceeds the ordinary swinging range for some reason to pass the limits of the reciprocating swinging range, that is, to reach a supporting point crossing position exceeding a linear positional relationship between the link arm and the link rod. For this reason, in the prior art, a limiting means may be provided to regulate the swinging movements exceeding the reciprocating swinging range.
An apparatus including such a limiting means has been disclosed in Japanese Examined Utility Model Publication No. 55-30758 or in Japanese Unexamined Utility Model Publication No. 7-31526. In the former apparatus, a spring, having one end portion connected to a body side, is connected to a link rod at its other end portion to bias the link rod, approaching a reversal position, in a reversing direction, thereby restricting the swinging from going beyond the reversal position. In the latter, a stopper is provided on a sleeve fixed to a body side pivotally supporting a wiper shaft to be rotatable around an axis, and when an wiper arm reaches a position exceeding the limit of the reciprocating swinging range, the wiper arm engages with the stopper to limit swinging.
There is a problem which arises with the former device in that, in addition to the original parts, the spring is necessary thereby increasing the number of parts and the structure becomes complicated making assembly troublesome. Moreover, since the link rod is always biased by the spring, a large-sized wiper motor for outputting greater power is needed making it difficult to achieve the purpose of providing a compact structure that is light in weight.
On the other hand, in the latter apparatus, in limiting the swinging of the wiper arm, a large load is placed on the sleeve having the formed stopper. Hence, it is necessary the sleeve have a larger strength. For this reason, the sleeve is made by an aluminium die-cast. Recently, to obtain light weight, compactness and cost reduction, the sleeve has been made of a resin. However, in the case that the aforesaid swinging limiting stopper is formed integrally with the resin-made sleeve, sufficient strength is unobtainable and, therefore, it is not directly useable.